In vehicles, particularly utility vehicles, closed-loop controls for a vehicle speed are known as speed-control system or alternatively as cruise control. These adjust the current vehicle speed to a reference speed which has been preset by the driver, without an actuation of the brake pedal being necessary. Systems of such a type can be expanded by an adaptive closed-loop control which additionally controls the vehicle speed by looking ahead and thereby presets a fuel-saving mode of driving for the purpose of attaining the reference speed. For the purpose of fuel-saving adaptive control, route information, in particular a topography of a route segment situated ahead, is taken into consideration for instance. A system of such a type is, for instance, known as a Predictive Powertrain Control (PPC) system.
In DE 10 2014 204 206 A1 a travel-path navigation with optimal speed profile is provided, wherein for a predefined distance from a first position of the vehicle as far as a destination an optimal vehicle speed is computed with the aid of dynamic programming. Consequently, for instance, at the start of a journey an optimal speed profile is drawn up which specifies the set vehicle speeds for respective places on the predefined route, so that the route can be followed with an optimized energy consumption. The speed profile in this connection is ascertained outside the vehicle, so that computationally intensive arithmetical operations are not executed in the vehicle.
US 2014/0277971 A1 likewise presents a method for computing a speed profile between a preset start-position and an end-position, wherein a route to be traveled between the start-position and the end-position is determined or preset. For this route to be traveled an optimal speed profile is drawn up, wherein route information—for instance, an uphill grade, speed limits, traffic jams, or similar—is taken into consideration. The computations in this connection are, for instance, executed and stored in advance on a computer or in a cloud, so that the speed profile ascertained in advance for the entire route can be used during the journey for the purpose of controlling the vehicle speed.
U.S. Pat. No. 8,386,091 B1 presents a comparable method for computing a speed profile, wherein the computation takes place outside the vehicle on a cloud-based computer. To this end, firstly a route to be traveled is preset by the driver, and for this route a fuel-saving speed profile is determined on the basis of route information.
A disadvantageous aspect in this connection is that the entire route to be traveled is computed, and consequently a lot of computation effort and computation time are necessary in order to determine the speed profile of the predefined route. In addition, the computation is based on current values prior to the start of the journey, so that in the case of an event during the journey, for instance a newly arisen or a dispersed traffic jam or an unintentional loading or unloading of the vehicle, the computed speed profile becomes imprecise.
In DE 10 2008 039 950 B4, moreover, a method is presented for ascertaining a driving profile. In this connection, a travel route that is to be followed is established, and the current position of the vehicle is ascertained. For the travel route or a part of the travel route, a speed profile is ascertained in a model, in particular as a function of a topography as well as properties of a drive device, for instance an acceleration potential, in order to obtain an optimization of consumption. Moreover, an acceleration at a distance ahead of the vehicle can be computed, in order to be able to overcome an uphill grade, for instance, in fuel-saving manner.
US 2012/0283928 A relates to a method for controlling an overspeed and an underspeed of a vehicle with a speed-control system during a downhill grade or an uphill grade. In this case, the vehicle speed and a vehicle mass are ascertained, and the brakes and the drive unit are set in such a manner that an overspeed or an underspeed can be minimized.
DE 10 2009 022 170 A1 relates to a method for limiting the vehicle speed as a function of a centripetal force acting on the vehicle. To this end, a curve situated within the capture range is detected by a capture unit, and for the capture range a centripetal force acting on the vehicle is determined, in particular as a function of a vehicle mass and as a function of the vehicle speed. If said force is too great, the vehicle speed is reduced.
In DE 10 2012 214 827 A1 a method is described in which the vehicle is controlled as a function of a loading parameter and as a function of route information which is determined in advance for a road section to be driven though.